Research in our laboratory has focused on the composition and metabolism of plasma lipoproteins (apo) in normal and dyslipoproteinemic man. Over the past 12 months we have completed studies utilizing radiolabeled high density lipoproteins (HDL), apoA-I, and apoA-II in 10 normals, 3 patients with type I hyperlipoproteinemia, and 2 patients with abetalipoproteinemia. The interaction of radiolabeled apoA-I and apoA-II with plasma lipoproteins, particularly HDL subfractions, has been of special interest. The 24 hour output and lipoprotein distribution of apoA-I and apoA-II in human thoracic duct lymph has also been characterized in six individuals undergoing thoracic duct drainage. Studies utilizing radiolabeled very low density lipoproteins (VLDL), apoC-II, and apoC-III2 have been completed in 7 normal subjects. Methodology for studying radiolabeled apoE kinetics in man has been developed. Ongoing computer analysis of data obtained in normal and dyslipoproteinemia subjects is nearing completion.